The fact that the guy I’m stood next to at the bar has the Punisher symbol tattooed on his arm is the first warning that tonight’s show at the Islington Academy is going to get pretty brutal.

There must be something in the water in Georgia, because this southern US state has managed to produce some of the best sludgy-pysch-stoner-concept-metal I’ve ever heard. The epicentre of this water poisoning seems to be the little city of Savannah, GA. from where both Circle Takes the Square and Kylesa hail.

Circle Takes the Square’s debut, ‘As the Roots Undo’, was released eight years ago. A DIY blend of experimental hardcore, metal and noise, it received great acclaim. Then they disappeared. I don’t know if there were ‘personal issues’ – there have been Spinal Tap-shaming line-up changes – but the core duo of Drew Speziale [guitars, vocals] and Kathy Stubelek [née Coppola – bass, vocals] remain.

Maybe the sheer scope, intricate wordplay and virtuoso musicianship of their debut just took a reeeeally long time to follow up. Dealing with existentialism, self-determination and self-realisation, fate and free will, it is one of the most ambitious metal records ever made. Eight years later, they’re playing ‘Decompositions Vol.1’, which, in their own words, explores the “boundaries between thinking and knowing, dreaming and waking, living and dying… a terrifyingly primal vision that bleeds through the fragile veil of consensus perception”. Deep? Yes. Complex, intricate and heavy? Certainly, but more importantly it’s also lots of fun.

With gymnastic leaps, they switch seamlessly between slow, delicate strumming, drums that almost stop dead, and gently harmonised vocals into a three-headed noise-hydra. Trading vocal leads between them, with Drew resembling some swivel-eyed Southern preacher at times, they have a definite sense of the theatrical, without being overly camp.

Kylesa offer a different kind of theatre all together. A Southern states psycho-drama, their name is derived from a Buddhist term for delusory states, and with two vocalists, cyclical stoner-rock riffs, time changes and two drummers sometimes playing perfectly in sync and sometimes subtly shifting to discombobulating effect, they are definitely designed to induce maximum sensory confusion.

Showing that there is more to their sound than brute force, tonight’s set is a triumph of skilled physicality. Deciding to give the audience a slow pummelling, rather than tearing them to shreds, Laura Pleasants and Philip Cope trade vocal duties as well as riffs, while the rhythm section (including those two drummers) work overtime. In fact, it seems like the whole band is fighting a battle to keep the room shaking at times. There are sweaty brows mopped left, right and centre, while behind them, for a little added dose of brutal intensity, the backdrop is a projection of bloody columns of spine and viscera, spiralling for infinity.

If I was the sort of person who went in for pathetic fallacy, Kylesa would be a humid swamp before a stormy night. Their sludgy psych-metal is the perfect fit for the heat and mugginess of Georgia’s sunken plantations, and a judicious use of theremin adds to the sense of the haunted American gothic. Although they don’t have the same single narrative thread running through their set, the titanic doomy Southern rock brings everything together. As they work their way through a back catalogue that blends Black Sabbath, blues, crust punk, psychedelia and the same sensibilities that have made fellow Georgians Mastodon lauded beyond the prog-metal world, Kylesa’s relative anonymity seems more and more ludicrous.

Tonight has been a very welcome return from one band, and a tour de force from another. May the South’s rock tradition rise again!